Daniel's profile - activity

Are you searching for the results by space or for an HVAC system, or for outdoor air?

Area and volume information are automatically calculated by DOE-2 based on the geometry model and are included in the ou

So the answer is that there isn't an easy way to do this in the eQUEST interface. If you want to create a custom view

You can use a schedule of type RESET to connect the operation of heating equipment to the outdoor air temperature. If yo

It's a little unclear which reports you are using. Are these variables selected in the hourly reporting schedules? I wou

It might be worth double checking the performance curves that you used for the VRF system. If you copy them into you .IN

It might help if you can share a picture or some details of the geometry that you are trying to change.

Unless it is a very small building, the building should be modelled with more than one zone. Different exposures (north,

What type of system is being used? Is there a schedule for outdoor air being applied to the system? Also, what question

Hello. If the zone is not cooled, then the report of unmet cooling hours is just reporting those occupied hours during w

In eQUEST you can model heat recovery from any chiller to a domestic hot water loop. If you open up the "Chiller Propert

Can you provide a few more details please? What is the system type? How is the zone modelled? Is it possible for you to

The zone heating load appears to increase when switching from four-pipe fan coils to water loop heat pumps I have create

My understanding (based on hearsay from the eQUEST user's list at onebuildilng.org) is that a new version of eQUEST is i

I don't understand how non-linear performance curves for the boiler would change the performance of the simulation. My u

To be more specific, you can simply multiply the overall efficiency for the fan by 15/20 to get the same full-load fan p

Note g on Table 11.3.2A states that water source heat pumps will be connected to a common water loop with heat rejection by an axial fan closed-circuit evaporative cooler. So I don't think the DX cooling means that the condenser on the individual heat pump is air cooled.

Assuming the cooling tower is water cooled?

You may need to add more information about your building to get a good answer to this question. At what time of day is the building peak in October? What directions do the various walls face? What is the window to wall ratio on each face of the building? What is the form of the building? Are there a lot of core zones which would be internal load dominated for cooling (wide floor plate) or are there more perimeter zones (narrow floor plate)?

When you say that the building peak load is in October, where are you getting this information from? Is it from the LS-C report? Does the building peak cooling load include outdoor air or is it for the envelope only? The LS-C report does not typically include the load for cooling ventilation air, which may be affecting the timing of the building peak.

As for your south facing zones, they will get more low angle sunlight in the winter than in the summer, and this is likely responsible for the higher cooling load in winter.

The curves should default to the correct curves from the library for an air-cooled condenser. I don't know if there is any way to change how the energy consumption is reported. You may be able to generate an hourly report for the chiller which shows which mode it is operating in and how much energy it is using to extract this information.

You seem to have hit upon a bug in eQUEST. I tried creating a heat pump chiller in a test model, and was unable to select "air-cooled" for the condenser type. In the DOE-2.2 Vol 2 Dictionary it specifically states that heat pump chillers can be either air cooled or water cooled (see page 189 under CHILLER, TYPE), and it appears that eQUEST should accept air cooled as an entry. I don't know how comfortable you are with the eQUEST input files, but I was able to get the model running correctly by editing the project.INP file in a text editor. I simply searched for the part of the file where the chillers are defined (do a search for "Chillers"). Then I changed the following line:

CONDENSER-TYPE   = WATER-COOLED

to

CONDENSER-TYPE   = AIR-COOLED

I also deleted the reference to the condenser water loop by removing the following line:

CW-LOOP = "Condenser Water Loop"

After making these changes, I reopened the file in eQUEST. The file opened without calling out any errors and I was able run the simulation and generate results.

So, in summary, it appears as though you can't select "air-cooled" in eQUEST, but you can model the heat pump chiller as air-cooled by editing the input file in a text editor.

It's a good thought. I would be tempted to try setting the EIR curve to a flat part-load curve, and leaving the capacity (as a function of temperature) as is. It's not clear to me how to handle the EIR (or COP). Presumably this would tend towards zero as there would be no compressor energy to speak of. I think the major challenge in this kind of work-around would be handling the loop water temperatures, as they would presumably need to be higher than usual to allow hot water coils to add sufficient heat to the supply air without a heat pump. I recommend setting up a model with a 4-pipe system and a separate model with a WSHP system with whatever workaround you are interested in trying. You should be able to determine the heating and cooling energy required from the HW and CHW loops on an hourly basis, and compare this to what happens in the WSHP loop to see if the results are making sense. If you spend enough time with the hourly reports you should be able to test out a few ideas and determine whether your workaround is giving realistic results.

In eQUEST you can model heat recovery from any chiller to a domestic hot water loop. If you open up the "Chiller Properties" window, under the "Basic Specifications" tab, look for Loop Assignments, and click on the drop down menu next to "HtRec". You should be able to select the DHW loop for heat rejection. Following 6.5.6.2.2, you may want to set the "Max Heat Recovery" to a ratio of 0.6 under the "Condenser" tab. This sets the keyword "MAX-HTREC" which sets the limit on the amount of heat reclaimed from the chiller on an hourly basis. You will need to make sure that the loop return temperature for the DHW loop is less than 95ºF to allow for heat recovery, but this is usually not a problem for DHW loops with low incoming water temperatures. You may also need to change the design temperature change of the water through the heat recovery heat-exchanger (DOE-2 keyword is HTREC-DT). The default is the LOOP-DESIGN-DT of the attached loop and it needs to be less than 70ºF. I recommend setting this manually, say to 30ºF to bring the temperature of the DHW from 55ºF to 85ºF. Unfortunately, the entry for this setting is greyed out in eQUEST, so you may have to open the .INP file and add the setting manually in a text editor. Alternatively, you could reduce the Loop Design DT for the domestic hot water loop to some number which is lower than 70ºF, making sure that the return temperature is less than 95ºF. So if the Design HW Temp for the DHW loop is 135ºF, you could set the Loop Design DT to 60ºF to get down to 75ºF return water temperature.

Good luck and let me know if you have any further questions.

P.S. You want to make sure you are not modelling recirculation on the loop, as this may lead to high return water temperatures which prevent heat recovery from working.

My understanding is that where components of the Proposed design are not specified or designed, these components should meet the requirements of the Baseline building. In this case, that would mean that the sizing factors in the Proposed should match the sizing factors in the Reference. See ASHRAE 90.1-2007, Table G3.1.10 (Proposed) HVAC Systems. "Where no heating/cooling system exists or no heating/cooling system has been specified ... System characteristics shall be identical to the system modeled in the baseline building".

This is a good idea. Even if the system has a properly sized heating capacity, a VAV system tends to be controlled with a constant central supply temperature with zone terminals increasing the flow under cooling and adding reheat under heating. If the supply temperature is constant and there is no zone heat it will be very hard to avoid unmet heating hours as some zones will be perpetually overcooled.

If the autosizing is not working it might be worth manually setting the heating capacity for the main VAV system. You might be able to pull the peak heating load for the system from the SS-J report in the .SIM file. This file can be accessed by going to the menubar > Tools > View Simulation Output. Once you have the peak heating load you could try sizing the heating capacity with whatever oversizing factor you are comfortable with.

I have also used global expressions based on a global parameter to resize the window height to change the window to wall orientation.

The eQUEST user's list is a fantastic resource with a vibrant and helpful community. Unfortunately it suffers from the problems common to many email lists that this website is trying to solve, namely that the archives are hard to find and search and that many common questions are often repeated. Hopefully by addressing eQUEST questions on this page we can encourage a slow build up of a community of eQUEST users here.

You can model this wall by creating two different walls at two different heights in the Detailed Edit mode of eQUEST. If you want to follow this path, I would recommend looking at the DOE2.2 Dictionary which is available on the eQUEST download page for details on how the geometry of exterior walls is defined. However, I think it would be much simpler to calculate the average R-value for the wall and stick with one wall type. I think that the differences in building loads and results would be very minor in either case.

Just to follow up in a more general way, the U-value of any construction can usually be adjusted by changing the thickness of the insulation layers in the detailed edit mode. You can select the construction, click over to the layers window and adjust the thickness of the insulation.

I recommend downloading the inputs developed by the Rocky Mountain Institute for modelling ASHRAE envelope constructions in eQUEST from this link. It's also worth checking out their page of energy modelling resources. Copy and paste the constructions into your .INP file, and modify the R-values until the U-value matches the required U-values from ASHRAE 90.1.

Thanks Julien for putting this out in the open!

You're most welcome. I'm not sure if there is such a document, I usually figure this out by right-clicking in the entry and going to "Item Help". So for example, if we are looking at the "Hot Deck max Leaving Temp", if you right click in the box where you would enter the temperature, and go to "Item Help" it will usually show you the DOE-2 name, in this case HEAT-SET-T. It should also open the item help in a help window, but I can't always get this to work on my computer so I usually just keep a PDF of the DOE-2 Dictionary open.

eQUEST by default does not create a central heating coil in variable volume systems. The default assumption seems to be that the mixed air temperature will be sufficiently warm that all heating can be done by the VAV boxes and/or baseboards in the zones. However, this assumption does not apply to cold climates! As you have noted in your question, setting the "Hot Deck Max Leaving Temp" to 95F corrects the above error message by forcing eQUEST to add a central heating coil to the system to heat the supply air. If you look at the DOE-2 Dictionary you will see that this activates the keyword "HEAT-SET-T = 95".

If you are jacking up the baseboards and the reheat terminals to address the unmet heating hours, it is possible that the boiler is autosizing to a much higher capacity than is necessary. If the boiler is oversized, this could cause the seasonal heating efficiency to be low and the heating energy consumption to be exaggerated. I recommend that you set the "Hot Deck Max Leaving Temp" to 65ºF (or whatever your VAV system supply air reset temperature is in heating mode), and reset the capacity of the VAV reheat boxes and baseboards to default to autosize their heating capacity. Run the model and look at the .SIM file to see what is happening with the unmet load hours and the boiler sizing. The SS-K report will show the unmet hours by zone which should allow you to figure out which zones are causing problems. I recommend using baseboards set to thermostatic control. The PV-A and PS-C reports will tell you what is happening with the boiler sizing and utilization. These reports should give you enough information to manually size the boiler near the peak heating load. Hopefully this will address the unexpectedly high heating energy.

Given the answers supplied below by Julien and crduggin, should the title be updated to be Daikin specific?

Note that the curve Julien is proposing uses identical numbers to the one supplied by Daikin, but different formatting to avoid having a line length longer than 80 characters.